In late March, he argued before the Supreme Court (PDF) against the constitutionality of the Obama administration’s health-care law. Earlier this month, he argued in federal court in Boston in favor of the 1996 Defense of Marriage Act (DOMA).

This time he was before the high court again, arguing that (PDF) Arizona’s controversial immigration law, SB 1070, was not preempted by federal law—even though the state law regulates and even criminalize acts in a traditionally federal field.

But defending DOMA in Boston, Clement made a different argument. In that case, he said, the federal government had not violated equal-protection rights when it defined marriage at the federal level—even though marriage was a topic the federal government had previously left to the states.

What explains the difference?

Clement is a highly respected lawyer with a sterling pedigree. After serving as Bush’s solicitor general, he became a partner at King & Spalding, a large firm that represents Coca-Cola, among other international corporate clients.

But he left the firm exactly a year ago Wednesday, after King & Spalding dropped its representation of the House Republican-led group defending DOMA. He moved to Bancroft PLLC, a more ideological, small firm founded by Viet D. Dinh—another Bush administration lawyer.

Of course, a lawyer has a right—even an obligation—to take different approaches in different cases, but recently Clement has seemed to turn himself into an ideological warrior for conservative causes.

No one is saying it out loud, but Clement’s federalism principles, whatever they may be, have shown themselves to be inconsistent when they bump up against his political ideology.

On Wednesday, defending the Arizona law, Clement told the Supreme Court justices that the lower appeals court that had partially halted its enforcement did so “only by inverting fundamental principles of federalism.”

The lower court was wrong, he said, to put the burden on Arizona to show that it had the authority to pass its law, rather than on the federal government. “[T]he burden is on the parties seeking to pre-empt a duly enacted state law to point to some provision in statutory law that does the pre-empting,” Clement said.

Defending DOMA, however, Clement painted the opposite picture, pointing to the “uniqueness of the dynamic that Congress was facing in 1996”—when Hawaii courts were considering whether same-sex couples were required to be allowed to marry under Hawaiian law.

In that case, Clement argued, the federal government was justified in attempting to “preserve its prior legislative judgments” by passing an unprecedented law that would impede upon the traditional role of the states in defining marriage.

Clement’s shifting federalism has surfaced in other ways in the arguments.

In Boston, he told the judges that when deciding between uniformity of federal law and deference to states’ historical role in defining marriage, the federal government could choose uniformity—even though attorneys for other parties pointed out that state laws defining marriage have never been uniform.

But on Wednesday, Clement said the opposite—that the federal government could not choose uniformity in the immigration context.

To Clement, it didn’t appear to matter that the federal government has traditionally created that law because, he told the justices, “[t]he State of Arizona bears a disproportionate share of the costs of illegal immigration.”

Meanwhile, when Clement argued on behalf of the states’ challenge to the Affordable Care Act last month, he found yet another argument: Despite the broad power Congress has to legislate interstate commerce, he told the high court, “The [health-care] mandate represents an unprecedented effort by Congress to compel individuals to enter commerce in order to better regulate commerce.”

Even Chief Justice John Roberts, a Bush appointee, questioned that argument, saying, “Well, Mr. Clement, the key to the government’s argument to the contrary is that everybody is in this market.”

Clement countered that the argument there depended on which market was being defined, but by the end, a court watcher could be forgiven for wondering what, exactly, Clement thinks federalism means.

Conservative judges and scholars—up to and including Antonin Scalia)—are fond of touting hard and fast legal principles to guide us through the muck of modern life, but the reality appears not to match the ideal. While Clement is highly respected for his legal acumen and unquestionably top-notch advocacy, all three of these high-profile cases—all of which involved political clients and causes—were aimed at sending legal rebukes to the Obama administration

It appears to be only this, and no coherent concept of federalism, that connects the dots.